1. Field of the Invention
The invention is directed to an improved throttle device for an internal combustion engine.
2. Description of the Prior Art
Throttle devices for internal combustion engines typically have a throttle valve shaft, which is pivotably supported in a throttle valve housing and onto which a throttle valve is integrally formed or secured. A gas duct extends through the throttle valve housing. Through the gas duct, air or a fuel-air mixture, for instance, can flow to an engine. The throttle valve opens and closes the gas duct by pivoting of the throttle valve shaft.
To keep the throttle valve from hitting the wall of the gas duct, it is known to set close tolerances for the mobility of the throttle valve shaft in its axial direction.
In the throttle device shown in German Patent Disclosure DE 39 24 611 A1, the throttle valve shaft is fixed in the axial direction, that is, the longitudinal direction of the throttle valve shaft, by a pin extending transversely through the throttle valve shaft.
In the throttle device shown in German Patent Disclosure DE 30 48 995 A1, the axial force transmission between the throttle valve shaft and the throttle valve housing is effected via a ball bearing built into the throttle valve housing.
In German Patent Disclosure DE 195 10 622 A1, a bearing means is press-fitted into the throttle valve housing, and a spring tenses the throttle valve shaft against this bearing means for the sake of exact axial positioning of the throttle valve shaft.
Depending on the material used, and particularly depending on the material used for the throttle valve housing, it can happen in the prior art that the axial support of the throttle valve shaft shifts, so that the unimpeded mobility of the throttle valve in the throttle valve housing at every temperature is no longer assured.